1. Technical Field
The subject matter described herein relates to wall mounted electrical control devices that can be remotely controlled and monitored via radio frequency transmissions. The subject matter described herein also relates to remote control devices for controlling and monitoring the wall mounted electrical control devices. More particularly, the subject matter described herein relates to electrical devices that can include one or more interchangeable key capsules, one or more associated interchangeable bezel frames which include a radio frequency antenna element, and one or more interchangeable radio frequency circuitry components.
2. Background Art
The field of home automation is rapidly developing. The ability to control electrical fixtures, appliances, and electronics remotely or through a central location is becoming more and more common place. Remote electronic control devices, such as lighting dimmers, include control circuitry and processors which can be powered by internal power supplies that derive power from high voltage house wiring that is typically 120 VAC (volts, alternating current) in the United States.
Wall mounted switching devices such as light switches and dimmers are typically placed inside a junction box or mounting fixture. In commercial construction, metal wallboxes are often used. A metal electrical wallbox along with a metal faceplate can act as a Faraday cage that significantly attenuates the transmission of radio frequency electromagnetic radiation from the antenna. As such, antenna location is an important factor.
Traditional radio Frequency (RF)—Controlled lighting dimmers have typically operated using RF frequencies, such as 418 megahertz (MHz), that have a relatively long ¼ wavelength (i.e. 6¾ inches) with respect to the physical dimensions of a residential single-gang wallbox that conforms to National Electrical Manufacturers Association (NEMA) specifications (i.e., 2¼ inches (W)×3¾ inches (L)×3¼ inches (D)). Those skilled in the art will recognize that the physical dimensions of an antenna, particularly the ‘length’ dimension, are primary determined by the ¼ wavelength (λ) of the operating frequency of the antenna. Various methods have been employed in the prior art to accommodate undesirable long antennas used to satisfy the ¼ wavelength (λ) standard at operational frequencies such as 418 MHz.
As an example, some traditional devices use a printed circuit board (PCB) antenna that includes capacitors to help balance the inherent inductive load. Prior art FIG. 1 depicts a wall mounted RF-controlled lighting dimmer 20, that incorporates a PCB antenna with dimensions much smaller than a ¼ wavelength (λ) of the intended operating frequency. This allows the antenna (not visible) to fit behind a faceplate 6 that covers the opening of a wall 7 cut to accommodate an electrical wallbox. A perimeter of the faceplate 6 includes left edges 31, right edges 32, top edges 33, and bottom edges 34. Prior art FIG. 2 depicts a wallbox 8 covered by a front surface 9 of a faceplate as part of an RF-controlled lighting control device according to a traditional system. The system includes a printed circuit board (PCB) antenna that fits behind a front surface of the faceplate and within the area defined by the faceplate. Prior art FIG. 3 shows a typical PCB antenna 24 that is used in traditional devices.
Prior art FIG. 4 illustrates an attempt to accommodate an extended wire antenna 242. As illustrated in FIG. 4, the extended wire antenna 242 extends for several inches outside of a wall-mounted electrical device, such as a lighting dimmer 20. As illustrated, the extended wire antenna 242 that extends from the lighting dimmer 20 is wrapped around the lighting dimmer 20 in order to conceal the extended wire antenna behind a faceplate 6 (indicated by the dashed lines). Such a solution is not practical for use behind a metal-faced faceplate, such as those typically found in residential kitchens and bathrooms, commercial buildings, etc.